1. Field of the invention
This invention relates, generally, to prosthetic locking devices. More particularly, it relates to a prosthetic lock of the ratchet type.
2. Description of the prior art
A prosthetic locking device is positioned at the distal end of a prosthetic socket. Its function is to enable releasable locking of a socket liner of the type worn on a residual limb to a prosthetic device such as an artificial leg and foot assembly. More particularly, an aperture is formed in a prosthetic socket at a distal end thereof for receiving a serrated, elongate locking pin therethrough. The elongate locking pin is engaged to the distal end of a socket liner. A locking means is positioned between the distal end of the socket and the proximal end of the prosthetic device. The locking means releasably engages the elongate locking pin, thereby interconnecting the socket liner and the prosthetic device.
There are two different types of prosthetic locking devices in current use. The first type is known as the ratchet type and the second is known as the clutch type. In a ratchet type lock, a serrated, elongate locking pin is selectively engaged by a pawl. In a clutch type, a serrated, elongate locking pin is engaged by the teeth of a movably mounted gear that can rotate only in one direction.
The primary drawback of a ratchet type lock derives from the distance between serrations; a socket slack is created whereby the residual limb moves up and down as the patient walks. Another drawback arises when a patient accidentally jams a prosthetic sock into the hole of the lock. The sock disables the ratchet and pawl locking mechanism and the socket can be removed only by cutting it off, thereby destroying it. This type of jamming is a very common occurrence.
The primary drawback of a clutch type prosthetic lock is that it has a greater height extent than a ratchet type lock, to accommodate the height of the one-way gear. Moreover, its operation is silent. Most amputees dislike this feature of clutch type locks because they prefer the reassuring clicking sound made by a ratchet type lock when it is positively engaged.
What is needed, then, is a ratchet type lock that provides a reassuring audible feedback when it is positively seated, but which has a low profile. Moreover, the new ratchet lock should enable removal of a residual limb from a socket, even if a prosthetic sock has become lodged in the locking means.
However, in view of the prior art in at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.
The longstanding but heretofore unfulfilled need for an improved ratchet type locking assembly is now met by a new, useful, and nonobvious invention. The novel locking assembly interconnects a prosthetic socket liner to a pylon that forms a part of a prosthetic leg. An elongate locking pin depends from a distal end of the socket liner and extends into releasable locking engagement with the novel lock assembly through an opening formed in the distal end of the prosthetic socket.
In all embodiments, the novel lock assembly includes two major parts that abut one another and which are held in such abutting relationship by suitable fasteners. Removal or at least loosening of the fasteners enables total or at least partial separation of said two major parts, respectively. When fully or partially separated, any jamming problems that may occur may be overcome in the absence of any need to cut the prosthetic socket.
The first major part may take the form of a laminating ring or a thermoforming plate. The former is used where the prosthetic socket is a carbon or fiberglass laminate and the latter is used where the prosthetic socket is a thermoformed plastic.
The second major part may take the form of a lock body with an integral pyramid for controlling the pylon or a lock body without a pyramid. Embodiments with integral pyramids save space and cost by combining the lock, mounting plate, and the pyramid or prior art deigns into a single piece. The embodiments with pyramids are subjected to side loads at heel strike.
The second major part may also take the form of a mounting plate with a pyramid or without a pyramid. The novel latch means that engages the elongate locking pin may be positioned within the first major part or the second major part of the lock assembly. Moreover, the lock assembly may be mounted within a prosthetic socket or externally thereof.
In a first embodiment, the novel prosthetic lock assembly for interconnecting a liner for a prosthetic socket with a pylon that forms a part of a leg prosthesis includes a first major part in the form of a laminating ring having a central bore formed therein. The central bore has a longitudinal axis substantially coincident to a longitudinal axis of the prosthetic socket liner. An elongate latching pin depends from the liner and is adapted to be slidingly received within the central bore. The elongate latching pin has a plurality of closely spaced apart, annular ratchet means formed therein along the length thereof. The annular ratchet means are disposed normal to a longitudinal axis of the elongate latching pin. As mentioned above, an opening is formed in the distal end of the prosthetic socket and the elongate latching pin extends through that opening to engage the novel lock assembly.
In the first embodiment, for use with laminated prosthetic sockets, the novel lock assembly includes a lock body having an integral pyramid. The lock body abuttingly engages a laminating ring and fastener means are provided for releasably interconnecting the laminating ring and the lock body. A latching means is formed in the lock body for releasably engaging an elongate latching pin. In this way, the socket liner is connected to the prosthetic device when the elongate latching pin is engaged by the latching means. Loosening or removal of the fastener means enables separation of the laminating ring and the lock body so that jamming of the latching means by a sock may be overcome in the absence of a need to cut off the socket.
A latching block that forms a part of the novel latching means is positioned in an opening formed in the lock body. The latching block is adapted to engage the elongate latching pin between contiguous ratchets of the annular ratchet means and to hold the elongate latching pin against longitudinal movement when so engaged. The opening has an extent in a preselected dimension greater than an extent of the latching block in a corresponding dimension so that the latching block has a first position at a first end of the opening, a second position at a second end of the opening, and an infinite plurality of positions therebetween.
A bias means is positioned within the opening and urges the latching block into engaging relation to the elongate latching pin when the bias means is in repose. A release means for overcoming the bias means is provided so that the elongate latching pin is removable from the lock body and hence from the laminating ring when the release means is activated.
The release means further includes a bore formed in an annular peripheral edge of the lock body. The bore is disposed radially with respect to the longitudinal axis of the prosthetic liner. A push button means extends through the bore and a first end of the push button means abuttingly engages the latching block and a second end of the push button means projects radially outwardly from the bore so that a user can press the second end of the push button means and displace the latching block, overcoming the bias of the bias means, thereby disengaging the latching block from the elongate latching pin so that the liner may be removed from the prosthetic socket.
In a second embodiment, the lock ring has no pyramid. In a third embodiment, used in conjunction with a plastic socket, a thermoforming plate replaces the laminating ring but the locking plate still has a pyramid. In a fourth embodiment, the thermoforming plate replaces the laminating ring and the locking plate has no pyramid.
All of the first four embodiments are mounted externally relative to the prosthetic socket. Four additional embodiments are disclosed, each of which is positioned within the prosthetic socket. In the final four embodiments, the latching block is positioned in an opening formed in the laminating ring or the thermoforming plate. Accordingly, the laminating ring in such embodiments is referred to as the laminating lock body and the thermoforming plate is referred to as the thermoforming lock body. The part corresponding to the lock body of the first four embodiments is referred to as a mounting plate with pyramid or a mounting plate without pyramid because it performs no locking function in said embodiments. However, it is releasably engaged to the laminating lock body or the thermoforming lock body with fasteners as in the first four embodiments. Thus, the anti-jamming feature is provided in all eight embodiments.
A primary object of this invention is to provide a ratchet type prosthetic locking device that does not require cutting of a socket when the locking device is jammed.
Another important object is to provide a ratchet type locking device so that users thereof are assured by audible clicking sounds that the device is working.
Another object is to provide such a device of the type that can be mounted inside or outside of a prosthetic socket and which may be provided with or without an integral pyramid for controlling a pylon.
Another important object is to provide a ratchet type locking device having a reduced longitudinal extent relative to ratchet type locking devices of the prior art.
These and other important objects, advantages, and features of the invention will become clear as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims.